The accumulation of residues on dental appliances (e.g., removable braces, retainers, dentures, etc.) is a familiar and persistent problem for wearers of such appliances. These residues often consist of some combination of food particles and biofilm (i.e., plaque), the latter of which is a slime layer that naturally develops when bacteria attach to an inert support. Many of these bacteria produce volatile sulfur compounds as waste products. If the dental appliance is not rid of food particles and biofilm on a regular basis, the malodourous waste products will accumulate, causing the wearer to exhibit bad breath. Even more serious is the potential for pathogenic bacteria to inhabit the biofilm, increasing the likelihood of infection for the wearer. Over time, the biofilm will be converted into dental calculus, which consists of inorganic mineralized salts derived from saliva, bateria, and food particles, as described in U.S. Pat. No. 6,670,312 B2.
In addition to accumulation of residues on the appliance, staining is another widespread problem reported by wearers of dental appliances. Staining of dental appliances is particularly pronounced among coffee and tea drinkers, smokers, and those who use chewing tobacco. Stained dental appliances are unsightly and can be a source of embarrassment for the appliance wearer, sometimes to the extent that the wearer foregoes wearing his or her dental appliance for the sake of vanity.
Although many wearers choose to brush their dental appliance with toothpaste (i.e., mechanical cleaning), others find it more convenient to soak their appliance in a cleansing solution. This cleansing solution is often generated by mixing a commercially available cleansing tablet or powder with water. Though such compositions have achieved considerable popularity and commercial success, there is a continuing need for improvement, especially with respect to plaque removal.
The majority of commercially available effervescent dental appliance cleansing tablets are based on alkaline peroxysalts (e.g., those sold under the tradename Efferdent®), which provide excellent bleaching action but poor plaque removal, as described in U.S. Pat. No. 4,552,679. An additional shortcoming of alkaline peroxysalts is their documented health risk. After seventy-three severe reactions and at least one death, the U.S. Food and Drug Administration issued a statement on Feb. 14, 2008 asking the manufacturers of denture cleansers to revise labeling and to consider appropriate alternatives to persulfate, a common alkaline peroxysalt found in many brands, including Efferdent®. All peroxysalts share a common mode of operation (i.e., liberation of hydrogen peroxide upon contact with water) and a similar structural feature (i.e., an associated molecule of hydrogen peroxide). Therefore, it is an object of the present invention to provide a dental appliance cleansing composition that does not include peroxysalts. Examples of powders and tablets incorporating alkaline peroxysalts can be found in U.S. Pat. Nos. 4,362,639, 4,552,679, and 5,486,304, and U.S. Patent Application 20070054830.
Sequestering agents are necessary to preserve surfactant activity in the presence of calcium and magnesium ions, which are present in dental plaque at 1.5% and 1.0%, respectively, on a dry weight basis [Gron, P., Yao, K., Spinelli, M. A Study of Inorganic Constituents in Dental Plaque. J. Dent. Res. Supplement to No. 5 1969, 48, 799-805.] Dental calculus is 30.7% calcium and 1.0% magnesium by weight, according to Encyclopaedia Chimica. Sequestering agents extract alkaline earth metal ions (e.g., calcium and magnesium ions) from the plaque or calculus by forming soluble complexes. This damages the structural integrity of the plaque or calculus, allowing it to be dissolved with the use of surfactants. Furthermore, these agents prevent the complexation of calcium and magnesium ions in the plaque or calculus with the surfactant, which would otherwise lead to surfactant inactivation.
U.S. Pat. No. 5,114,647 to Levesque et al. teaches the preparation of a rapidly dissolving tablet for sanitizing water bodies that consists of an alkali metal cloroisocyanurate bleaching agent admixed with granules of alkali metal carbonate and water-soluble carboxylic acid for effervescence. To enhance cleaning action, the incorporation of a surfactant is also taught. This composition, however, lacks a sequestering agent.
Similarly, in U.S. Pat. No. 6,099,861 to DeSenna et al., a water soluble effervescent tablet formulation is disclosed that contains a bromide releasing agent and a hypochlorite releasing agent. While this tablet offers good disinfecting power over a wide pH range, it also does not contain a sequestering agent for alkaline earth metal ions.
The use of complex phosphates as sequestering agents for alkaline earth metals such as calcium and magnesium in dental plaque is described in U.S. Pat. No. 2,409,718. Though the composition combines the bleaching power of a peroxysalt with a sequestering agent to facilitate plaque removal, it is also known to require 2,2′-dihydroxy-3,5,6,3′,5′,6′-hexachlorodiphenylmethane(hexachlorophene), a disinfectant, to achieve these cleaning properties. Hexachlorophene has recently been shown to be toxic in neonates [Kimbrough, R. D. Review of the toxicity of hexachlorophene, including its neurotoxicity. J. Clin. Pharmacol. 1973, 13, 439-451.], and its use has been limited. The patent teaches that this component is unique and that no alternatives are known. Furthermore, the composition requires the use of a peroxysalt.
U.S. Pat. No. 6,670,312 B2 to Sugimoto et al. teaches the removal of dental calculus using a hydroxycarboxylic acid and sulfamic acid. These agents act very slowly, requiring 24 hours to remove a scale deposit of calcium and magnesium. In addition, the agents are not known to demonstrate bleaching activity.
U.S. Pat. No. 3,293,188 to Brown et al. teaches the preparation of a sterilizing and disinfecting powder consisting of a dichlorocyanurate with “a synergistic carrier agent mixture” of sodium tripolyphosphate and sodium sulfate decahydrate. The high temperature required to prepare this mixture and the presence of water causes significant decomposition of the dichlorocyanurate, however, which results in a corresponding decrease in the available chlorine content of the product, as described in U.S. Pat. No. 3,872,118. Consequently, the low concentration of available chlorine (75 ppm) generated upon dissolution of this powder in water is insufficient for dental appliance bleaching, and the composition is not known to have any plaque removal properties.
U.S. Pat. No. 3,936,385 to Cheng teaches the preparation of an effervescent denture cleanser composition consisting of a chlorine compound which liberates hypochlorite chlorine on contact with water, and a peroxysalt. The pH of the composition dissolved in water must be at least 9 . At pH 9 and above, the free chlorine generated upon dissolution of the composition exists almost entirely (>95%) as the hypochlorite anion (OCl−), with a balance of hypochlorous acid (HOCl). According to U.S. Pat. No. 6,099,861, the hypochlorous acid form is known to be the antimicrobial form, while the hypochlorite form exhibits only modest antimicrobial properties. The lower antimicrobial activity of hypochlorite is attributed to its negative charge, which is believed to inhibit its diffusion through the cell wall of microorganisms.
U.S. Pat. No. 3,936,385 also discloses the use of oxidizable dyes in an effervescent denture cleansing composition. Upon contact of the formula with water, these dyes slowly react with the bleaching agent, which causes the solution to change color. Eventually the cleansing solution loses its color completely. This system serves as a time lapse indictor and signals to the user the appropriate time to remove the dental appliance from the cleansing solution.
There remains a need for a safe and convenient composition that is effective for bleaching, disinfecting, deodorizing, and removing plaque and other residues from a wide variety of dental appliances.